Contrary to previous thinking, micronutrient malnutrition is not uniquely the concern of poor countries. While micronutrient deficiencies are certainly more frequent and severe among disadvantaged populations, they do represent a public health problem also in most industrialized countries where obesogenic unbalanced diets have a major impact on macro- and micronutrients. Worldwide micronutrient intakes do not fit pregnancy requirements.

Since 1989 it has been shown that dietary surveys of pregnant women in industrialized countries consistently demonstrate Fe intake well below current recommendations. A recent review [6] summarizes the best available evidence related to the food-derived vitamin and mineral intakes of pregnant women in developed countries demonstrating that folate, iron, and vitamin D intakes are consistently below nutrient recommendations in each geographical region. In particular, despite folate recommendations varying across geographical regions, average folate intakes in all regions were between 13 and 63 % lower than recommendations. Similarly, iron intakes reported by pregnant women were below nutrient recommendations in almost all developed regions. However, these results underestimate the number of pregnant women who met national pregnancy micronutrient targets on the basis of combined food and supplement intakes.

Moreover, many micronutrients with important roles during pregnancy (e.g., iodine) were not commonly reported within the included studies, and thus, nutritional adequacy could not be evaluated. In the last 10 years, median urinary iodine below the recommended values has been reported in pregnant women of many countries in the world (Argentina, Greece, Italy, Wales, Ireland). However, there are no studies about a potential role of iodine in the great obstetrical syndromes.

In fact, although a balanced diet is generally accessible in industrialized countries, a switch to highly processed energy-dense but micronutrient-poor foods is likely to adversely affect micronutrient intake and status.

The ideal definition of a physiological requirement is the amount and chemical form of a nutrient that is needed systematically to maintain normal health and development without disturbing metabolism of any other nutrient. The physiological requirement is very difficult to be estimated, and for this reason micronutrient requirement is defined as the minimum amount needed by an individual to avoid deficiency.. However, micronutrient recommendations are designed for populations or subgroups of populations, and they are defined as intakes of micronutrients sufficient to meet the requirements of the majority of healthy individuals (generally 97.5 %) of that population or group.

Many countries have developed recommendations for intake of micronutrients in the normal diet. However, there is considerable variation in the recommended micronutrient intakes used by countries in particular within Europe, partly due to different methodologies and concepts used to determine requirements and different approaches used to express the recommendations. The EURRECA Project was designed in Europe. Specifically, the EURopean micronutrient RECommendations Aligned (EURRECA) Network of Excellence has worked to provide an evidence-based framework for establishing micronutrient requirements. EURRECA is a network of excellence funded by the European Commission and established to address the problem of differences between countries in micronutrient recommendations [15].

First of all the EURRECA network developed a selection process to identify a list of micronutrients to focus on. The prioritization of micronutrients was based on the availability of new scientific evidence, the public health relevance, and the heterogeneity of the recommendations [10]. Ten micronutrients were identified as most urgently in need of review: vitamin D, iron, folate, vitamin B12, zinc, calcium, vitamin C, selenium, iodine, and copper. Of these, vitamin C, vitamin D, folate, calcium, selenium, and iodine were the nutrients showing a higher prevalence of inadequate intakes in Europe. In particular, a lack of harmonized and evidence-based recommendations was found for the supply of vitamin D, folate, and iron during pregnancy, lactation, and infancy [21].

Preeclampsia is one of the leading causes of maternal morbidity and mortality and preterm delivery in the world. Nutritional interventional studies to prevent hypertension and different end-organ diseases grouped under the same syndrome are biased by the different prevalence of clinical phenotypes that are the results of various pathological process. Abnormal placentation with release of anti-angiogenetic factors in the maternal circulation, together with a predisposed maternal phenotype, seems to be involved. In particular, preeclampsia is associated with an increased inflammatory state, but the role of maternal nutrition in influencing the risk of developing preeclampsia is unclear.

Low body mass index (BMI) before pregnancy and inadequate body weight gain of pregnant women in the second and third trimesters have been shown to be significantly associated with spontaneous preterm delivery in the USA and in Europe. Moreover, recent data obtained in 66,000 women in Norway showed that high scores on the “prudent” dietary pattern in the first months of pregnancy are associated with significantly reduced risk of preterm delivery hazard ratio [16]. This dietary pattern is characterized by intake of vegetables, fruit, whole grains, fish, and water, suggesting higher intake of micronutrients.

In this context, several studies suggest that multivitamin and mineral use before and during pregnancy may potentially prevent preterm birth. However, there is still not enough evidence to support multivitamin supplementation for reduction of preterm delivery.

A trial by Catov et al. [8] demonstrates a reduced risk of preterm delivery and small for gestational age in a cohort of 1,823 women who reported periconceptional multivitamin use, even if this finding was limited to women with a BMI <30. In 2011 data from more than 35,000 women in the Danish National Birth Cohort [9] confirmed that women who reported periconceptional multivitamin use had a reduced risk of preterm birth and a reduced risk of SGA (<5th percentile). The risk of an SGA birth was reduced in multivitamin users regardless of their prepregnancy BMI, with the strongest association in regular users in the post-conception period. However, these findings should be interpreted with caution because multivitamin use also correlated strongly with other lifestyle factors.

Although mechanisms that may link periconceptional multivitamin use to preterm delivery are not understood, impaired placentation seems to be implicated. Placentation is characterized by vascular remodeling, oxidative stress, inflammation, and rapid cell division, all of which may be affected by nutritional status. During pregnancy, oxidative stress has been implicated not only in the pathophysiology of preeclampsia but also of preterm birth leading to poor birth outcome. Moreover, hyperhomocysteinemia, as a consequence of altered micronutrients like folic acid and vitamin B12, is associated with increased production of reactive oxygen species that generate oxidative stress. One case–control study related the preconception sufficiency of vitamins B6 and B12 in maternal serum to a 50–60 % reduced risk of a PTB. Nevertheless a large prospective national birth cohort study in Norway did not find a protective effect of dietary folate intake or folic acid supplementation on spontaneous preterm delivery in uncomplicated pregnancies [33].

Mothers in low-income countries frequently have inadequate micronutrient intakes. They often consume inadequate levels of micronutrients due to limited intake of animal products, fruits, vegetables, and fortified foods. Low birth weight (LBW) is common in undernourished populations in low- and middle-income countries, predominantly because of intrauterine growth restriction. Micronutrient supplementation and fortification are currently being used as strategies to improve nutrition even in resource-poor settings since many girls and women are chronically undernourished. Many trials have assessed the effect on birth weight of giving women of low socioeconomic status micronutrient supplements during pregnancy.

In 2001 the Pune (India) Maternal Nutrition Study showed the lack of association between size at birth and maternal energy and protein intake but strong associations with folate status and with intakes of foods rich in micronutrients that suggested that micronutrients may be important limiting factors for fetal growth in this undernourished community [30]. However, in another trial performed in the Indian population, a daily snack providing additional green leafy vegetables, fruit, and milk before conception and throughout pregnancy had no overall effect on birth weight. Subgroup analyses indicated a possible increase in birth weight if the mother was supplemented >3 months before conception and was not underweight.

In the USA a prospective cohort study of 1,116 low-income and minority pregnant women showed that suboptimal maternal calcium intake and vitamin D status might affect fetal growth [32]. Studies in India have shown a low dietary consumption of vitamin B12 due to dietary pattern of vegetarianism and poor consumption of milk and milk products. In vegetarian Indians, deficiency of vitamin B12 is commonly seen, while concentrations of folate are adequate. Together with folic acid, vitamin B12 is also an important determinant of fetal growth and development. During pregnancy, the increased requirement of folic acid is met with supplementation, while vitamin B12 remains untreated and possibly deficient. In addition to vitamin B12 and folate deficiencies alone, there may be adverse birth outcomes associated with unbalanced vitamin B12 and folate intakes or status during pregnancy. Folate to vitamin B12 ratio was correlated to neonatal anthropometric measures. Imbalance in the maternal micronutrients with increasing ratios of folate to vitamin B12 was associated with an increase in plasma homocysteine and lowering of neonatal birth weight, birth length, head circumference, and chest circumference, while no significant association to other anthropometrics was observed.

In 2009 a meta-analysis on original data from 12 randomized, controlled trials concluded that compared with iron–folic acid supplementation alone, maternal supplementation with multiple micronutrients during pregnancy in low-income countries resulted in a small increase in birth weight and a reduction in the prevalence of LBW of about 10 %. The effect was greater among women with higher BMI [18].

A recent meta-analysis of 21 randomized controlled trials on the effects of multiple supplementation on pregnancy outcome found that low-/middle-income women who received multiple supplements had a significant reduction in the risk of SGA offspring compared with women who received iron/folate supplements alone also in developing countries [19]. However, this study failed to show a significant impact on any of the other outcomes of pregnancy. The Generation R Study in Rotterdam provided evidence that low adherence to the Mediterranean diet in the periconceptional period significantly increased the risk of intrauterine growth restriction [37].